NUMERICAL MODELING OF A PLANAR UNCONFINED OBLIQUE JET MOVING ALONG THE GROUND SURFACE

Power-Augmented-Ram (PAR) and Vertical/Short Takeoff and Landing (V/STOL) vehicles use jet support at low speeds when the passive aerodynamic lift is not sufficient. Although V/STOL aircraft have been previously investigated, the PAR concept requires further understanding of the obliquely impinging jet. Previous modeling studies on jet impingement considered jets exiting from domain boundaries. However, many jet applications are not confined in the upward direction and require modeling of airflow entering the jet source. The unconfined jet, modeled as a ducted momentum source, is investigated in this work. The computational approach consists of a two-dimensional, steady, incompressible finite volume method utilizing the k-epsilon turbulence model. The numerical approach is validated for the planar turbulent free jet, jet normally impinging on the ground, and jet entering a channel under a ground-effect platform. New results are obtained for obliquely impinging jets moving along the ground. Flow structures are studied with focus on the upstream ground vortex, jet entrainment, downstream momentum flow, and effects of jet translating through a stagnant fluid. Beneficial aerodynamic configurations, which reduce ingestion and maximize downstream momentum flow, suggest small impingement angles and moderate ground distances.